$(document).ready( function() {
  $(".thumbnail img").click( function() {
    var changeSrc = this.src;
    $(".target img").attr("src", changeSrc);
  });
});

$(document).ready( function() {
  $(".thumbnail2 img").click( function() {
    var changeSrc = this.src;
    $(".target2 img").attr("src", changeSrc);
  });
});